1. Field
Acknowledgments, including affirmative acknowledgments (ACK) and negative acknowledgments (NACK), can be transmitted on a physical uplink control channel (PUCCH). Such acknowledgments relate to one or more codeword transmitted on a physical downlink shared channel (PDSCH) in the case of carrier aggregation. Certain embodiments of the present invention relate to channel selection when carrier aggregation is used.
2. Description of the Related Art
In long term evolution (LTE) release 8 (Rel-8) time division duplexing (TDD), in the case of an asymmetric downlink (DL)/uplink (UL) configuration, the user equipment (UE) has the possibility to report ACK/NACK associated with multiple downlink subframes during one uplink subframe. The ACK/NACK signaling for multiple downlink subframes can be made using either ACK/NACK bundling or ACK/NACK multiplexing mode.
For ACK/NACK bundling mode, the ACK/NACK bits can be first bundled in the time domain to get one bit, or 2 bits with multiple codeword (MCW) downlink transmission. Then the ACK/NACK bits can be modulated and transmitted on the physical uplink control channel corresponding to the last detected downlink grant.
For ACK/NACK multiplexing mode, channel selection can be used. Channel selection enables transmission of 2-4 bits via a single physical uplink control channel. The selected channel and the QPSK constellation point used can be determined based on the ACK/NACK/DTX states for the multiple downlink subframes as shown in Table 10.1-2, 10.1-3, and 10.1-4 of 3GPP TS36.213 v850.